The principle of floatation states that when an object floats on a liquid the buoyant force that acts on the object is equal to the weight of the object.
If the weight of the object is less than the upthrust, then the object will float on the fluid.
If the weight of the object is greater than the upthrust, then the object will sink in the fluid.
If the weight of the object is equal to the upthrust, then the object will float with half of its body immersed.